The present invention relates to novel tetrahydroxanthone derivatives, and more particularly to a tetrahydroxanthone derivative represented by the following general formula (I): ##STR4## wherein R is a hydrogen atom, a hydroxyl, cyano, lower alkyl, lower alkoxy, lower acyloxy, benzoyloxy or tetrazolyl group, or ##STR5## (R.sub.3 is a hydrogen atom, and R.sub.4 is a hydrogen atom, a phenyl group which may be optionally substituted, or a tetrazolyl group; or R.sub.3 and R.sub.4 commonly form a ring together with the adjacent nitrogen atom and another nitrogen atom or an oxygen atom); R.sub.1 is a hydrogen or halogen atom, a lower alkyl, cyano, carboxyl or tetrazolyl group, or ##STR6## (R.sub.5 is a hydrogen atom, and R.sub.6 is a phenyl group which may be optionally substituted, or a tetrazolyl group; or R.sub.5 and R.sub.6 commonly form a ring together with the adjacent nitrogen atom and an oxygen atom); and R.sub.2 is a hydrogen or halogen atom, or a lower alkyl group; with the proviso that neither R nor R.sub.1 is a hydrogen atom; when R is --CONH.sub.2, R.sub.1 and R.sub.2 are not respectively a hydrogen atom nor a hydrogen or halogen atom, or a lower alkyl group; and R.sub.2 and R.sub.1 are not respectively a hydrogen atom nor a halogen atom or a lower alkyl group.
Tetrahydroxanthone derivatives having the formula (I) according to the present invention exhibit anti-allergic, anti-inflammatory, analgesic and inhibitory effects on PCA (Passive Cutaneous Anaphylaxis) and hence are extremely useful as pharmaceutical products.